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When you hit the
launch button, this
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is the screen that you'll see.
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Before we start
doing the exercise,
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let's first look
at the controls.
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In the upper left-hand
corner, we have a zoom bar.
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If you hit the plus (+)
button, you will zoom in.
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If you hit the minus (-)
button, you will zoom out.
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You can also drag this
or use the scroll button
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on your mouse.
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In the upper right-hand
corner is a Greyscale button
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and an Interpretation button.
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Greyscale, seen here, shows
you a geophysical plot
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overlying a satellite map.
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The Interpretation
button is a drawing
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of that geophysical plot.
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Below the Greyscale and
Interpretation buttons
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is a slider that influences
the transparency.
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All the way to the
left, fully transparent.
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All the way to the right,
you get a solid image.
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And in the middle, between,
is something semi-transparent.
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Now let's do some
interpretation.
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First, click on the Greyscale
button and locate the slider
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all the way to the left
on full transparency.
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Can you see any of the
archaeological features
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in this image?
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The rectangular shape
of the fort is visible,
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but there's very little of
the extra-mural settlement
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in this area that can be seen.
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Now move the slider to
its halfway position,
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or thereabouts.
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Now you can see the overall
size of the settlement inside
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and outside of the
fort walls relative
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to the modern landscape.
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Now zoom into an area
for closer inspection.
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And then move the slider
all the way to the right
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to reduce the transparency.
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You will see that while
some of the lines revealed
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by geophysical
survey are still very
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visible and clear, for example
here, many of these features
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become less distinct.
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Staying at the same
zoom and transparency,
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click on Interpretation.
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This should help to reduce
the fuzziness or noise
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of the geophysical survey by
indicating the results that
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relate to structures, mostly
roads, walls, and ditches.
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Remember, though, that this
drawing is an interpretation
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of the geophysical
survey results,
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and a different
surveyor may be more
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or less confident in their
interpretation of some
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of these features.
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If you zoom out a bit,
hopefully the interpretation
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will resolve into a pattern
that is easier to understand.
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The black outlines ditches,
which often formed boundaries
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between plots of land, while
grey shows the outlines
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of buildings and
other structures.
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Black blobs are pits or holes.
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Sometimes a lack of
indication can also be useful.
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For example, let's
look at the fort.
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The break in the
ditches and banks
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show the location of a road
and gate into the fort.
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Or these squarish blocks
in a rectangular shape here
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indicate the
presence of a barrack.
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To the southeast of the
fort is a native settlement.
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Press the Iron Age Settlement
button to the right
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if you need help
locating this feature.
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Here you can see the Iron Age
settlement outlined in a pink
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box, remembering that the
negative anomalies are black
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and the positive
anomalies in grey.
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Sometimes, though,
geophysics does not always
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reveal clear results.
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Click the Temple
button to the right
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of the screen to locate
Roman temples that
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were discussed in week 4.
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The location of the
temples, outlined here
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in the pink circle, has been
known from previous excavation.
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But note the general shape
or outline of the temple
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is not seen in the geophysical
survey
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or the interpretation plot.
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While there's no
substitute for excavation,
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the layering and interrogation
of evidence in this form
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is significant when it comes
to interpreting a site without
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or even before putting
a spade in the ground.
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Now it's your turn.
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